bonding: permit using arp_validate with non-ab modes

Currently it's disabled because it's sometimes hard, in typical configs, to
make it work - because of the nature how the loadbalance modes work - as
it's hard to deliver valid arp replies to correct slaves by the switch.

However we still can use arp_validation in loadbalance with several other
configs, per example with arp_validate == 2 for backup with one broadcast
domain, without the switch(es) doing any balancing - this way we'd be (a
bit more) sure that the slave is up.

So, enable it to let users decide which one works/suits them best. Also
correct the mode limitation from BOND_OPT_ARP_VALIDATE.

CC: Nikolay Aleksandrov <nikolay@redhat.com>
CC: Jay Vosburgh <fubar@us.ibm.com>
CC: Andy Gospodarek <andy@greyhouse.net>
Signed-off-by: Veaceslav Falico <vfalico@redhat.com>
Acked-by: Nikolay Aleksandrov <nikolay@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Documentation/networking/bonding.txt

@@ -270,9 +270,9 @@ arp_ip_target
 arp_validate
 
 	Specifies whether or not ARP probes and replies should be
-	validated in the active-backup mode.  This causes the ARP
-	monitor to examine the incoming ARP requests and replies, and
-	only consider a slave to be up if it is receiving the
+	validated in any mode that supports arp monitoring.  This causes
+	the ARP monitor to examine the incoming ARP requests and replies,
+	and only consider a slave to be up if it is receiving the
 	appropriate ARP traffic.
 
 	Possible values are:

drivers/net/bonding/bond_main.c

@@ -4183,10 +4183,6 @@ static int bond_check_params(struct bond_params *params)
 	}
 
 	if (arp_validate) {
-		if (bond_mode != BOND_MODE_ACTIVEBACKUP) {
-			pr_err("arp_validate only supported in active-backup mode\n");
-			return -EINVAL;
-		}
 		if (!arp_interval) {
 			pr_err("arp_validate requires arp_interval\n");
 			return -EINVAL;

drivers/net/bonding/bond_options.c

@@ -151,7 +151,8 @@ static struct bond_option bond_opts[] = {
 		.id = BOND_OPT_ARP_VALIDATE,
 		.name = "arp_validate",
 		.desc = "validate src/dst of ARP probes",
-		.unsuppmodes = BOND_MODE_ALL_EX(BIT(BOND_MODE_ACTIVEBACKUP)),
+		.unsuppmodes = BIT(BOND_MODE_8023AD) | BIT(BOND_MODE_TLB) |
+			       BIT(BOND_MODE_ALB),
 		.values = bond_arp_validate_tbl,
 		.set = bond_option_arp_validate_set
 	},